Fat for Vitamin Absorption. How much really?

my mom, alongside many more people, consumes olive oil and fat along side a fruit smoothie claiming that the fat is needed for vitamin absorption. The question lays how much fat do you need to intake with your meal in order to have a high absorption of vitamins in your bloodstream?

DO you know any good studies demonstrating the effect of extra fat intake on vitamin fat-soluble vitamins (A,D,E,K)?